Wwordpress wp downloadmanager - error in send license key to client - urgent repost

We have a woocommerce site all working with products and payments... The site lets users buy software, when someone buys the software the license key is meant to be sent to them. But currently it’s not. It has been working, but we had to upload a backup version, now it doesn't work. We are using the 'Download Manager' plugin. Each product shows licence key, just doesnt get sent to the client.